Hi, thanks for using Healthcare Magic. Rituxan contains rituximab, one of the known monoclonal antibody that used to treat cancer in lymphatic system such as lymphoma or systemic lupus erythematous. Like any other drugs, this drug had several side effects including joint pain. Call your doctor right away if you start to have a cough that won t go away, weight loss, night sweats, fever, chills, flu-like symptoms (such as a runny or stuffy nose, headache, blurred vision, or feeling generally ill), painful or difficult urination, or sores, ulcers, or white spots in the mouth or on the lips. These may be signs that you have an infection. Take care.